The removal of H2S and other sulfhydryl compounds from a liquid or gaseous hydrocarbon stream is a problem that has challenged many workers in many industries. One such industry is the petroleum industry, where the H2S content of certain crudes from reservoirs in many areas of the world is too high for commercial acceptance. The same is true of many natural gas streams. Even where a crude or gas stream contains only a minor amount of sulfur, the processes to which the crude oil or fractions thereof are subjected often produce one or more hydrocarbon streams that contains H2S.
The presence of H2S in hydrocarbon streams presents many environmental and safety concerns. Hydrogen sulfide is highly flammable, toxic when inhaled, and strongly irritates the eyes and other mucous membranes. In addition, sulfur-containing salts can deposit in and plug or corrode transmission pipes, valves, regulators, and the like. Flaring of natural gas that contains H2S does not solve the problem for gas streams because, unless the H2S is removed prior to flaring, the combustion products will contain unacceptable amounts of pollutants, such as sulfur dioxide (SO2)—a component of “acid rain.”
Hydrogen sulfide has an offensive odor, and natural gas containing H2S often is called “sour” gas. Treatments to reduce or remove H2S from hydrocarbon or other substrates often are called “sweetening” treatments. The agent that is used to remove or reduce H2S levels sometimes is called a “scavenging agent” or “scavenger”. The sweetening or scavenging of H2S from petroleum or natural gas is only one example of where H2S level reduction or removal must be performed. Many aqueous substrates also must be treated to reduce or remove H2S.
In the manufactured gas industry, or the coke-making industry, the destructive distillation of bituminous coal with a high sulfur content commonly produces coal gas containing an unacceptable amount of H2S. Another H2S contamination problem arises during the manufacture of water gas or synthesis gas. Water gas or synthesis gas streams that contain H2S often are produced by passing steam over a bed of incandescent coke or coal. The incandescent coke or coal often contains a minor amount of sulfur, which contaminates the resulting gas stream.
The problem of removing or reducing H2S from hydrocarbon and aqueous substrates has been solved in many different ways in the past. Most of the known techniques involve either (a) absorption, or selective absorption by a suitable absorbent, after which the absorbent is separated and the sulfur removed to regenerate and recycle the absorbent, or (b) selective reaction with a reagent that produces a readily soluble product. A number of known systems treat a hydrocarbon stream with an amine, an aldehyde, an alcohol, and/or a reaction product thereof. The wide variety of processes, patents, and publications that describe methods for removing H2S from hydrocarbon streams is evidence that it is desirable and necessary to remove H2S from aqueous and hydrocarbon streams.
A continuing need exists for alternative processes and compositions to reduce and/or remove H2S from aqueous and hydrocarbon substrates. The need for removing sulfhydryl compounds from hydrocarbon substrates has increased as the world's supply of “sweet” natural gas and crude oil is reduced. It would thus be desirable to discover and/or develop new scavenging agents that are fast and have a high capacity for removing sulfhydryl compounds as compared with known scavengers.